Spring-driven time-delayed switch-operating device



Aug. 4, 1964 A. POWELL 3,143,616

SPRING-DRIVEN TIME-DELAYED SWITCH-OPERATING DEVICE Filed Feb. 15, 1961 Sheets-Sheet 1 A Home 2 United States Patent 3,143,616 SPRING-DRIVEN TIlVIE-DELAYED SWITCH- OPERATING DEVICE Anthony Powell, London, England, assignor, by mesne assignments, to Seemark Switches Limited, Cardiff, England, a British company Filed Feb. 13, 1961, Ser. No. 88,949 Claims priority, application Great Britain Feb. 12, 1960 11 Claims. (Cl. 200-422) This invention relates to electric timing devices and especially safety cut-outs.

An object of the invention is to provide a comparatively simple means of interrupting an electrical circuit after a period of time has elapsed. It is not intended to provide accurate timing, but primarily to prevent circuits being left switched on for long periods inadvertently.

According to the present invention, there is provided an electrical timing device or cut-out comprising a heatsensitive element, electrical heating means therefor and electrical contacts arranged to be operated by thermal movements of the heat-sensitive element whereby said element alternately is heated and cools and the contacts alternately open and close so long as an electrical supply is available thereto, in combination with main switch operating means including a pawl or detent member connected with the heat-sensitive element and a stepwise moving member cooperating with the pawl or detent and arranged to move a step at a time as successive thermal movements are performed by the heat-sensitive element, a main switch being operated after the stepwise moving member has moved apreselected number of steps.

In one form, the stepwise moving member can be a ratchet wheel which is driven a step at a time by a pawl that moves to and fro as the heat-sensitive element expands and contracts. In another arrangement, the stepwise moving member can be a spring-driven toothed escapement wheel, with the eXpansion and contraction movements of the heat-sensitive element actuating a detent member cooperating with the wheel teeth.

. A practical embodiment of the invention will now be described in more detail by way of example, and with reference to the accompanying drawings, in which:

FIGURE 1 is a front elevation of the unit to be described,

FIGURE 2 is a rear elevation with a rear cover removed and a sub-assembly of the unit shown in broken lines only,

FIGURE 3 is a view of the sub-assembly shown in broken lines in FIGURE 2, to a larger scale and viewed in the direction of the arrow 3 of FIGURE 2,

FIGURE 4 is a detail of switch contacts of the assembly of FIGURE 3, toan enlarged scale and seen in the direction of the arrow 4 of FIGURE 3, and

FIGURE 5 is. a detail of part of the assembly of FIGURE 2, seen in the direction of the arrow 5 of FIGURE 2.

In the drawings there is shown a unit arranged to serve duty as a 13 ampere switched socket outlet for wall mounting and incorporating a timing device according to the invention. FIGURE 1 shows the front of the unit, where are provided in a fascia plate 34 the plug pin re ceptor holes 11, a lamp 12 to indicate when the socket is live, and two control push buttons 13, 14.

In FIGURE 2 the back of the unit is shown but with the back cover removed and the timing sub-assembly 15 shown in broken lines only. A block 24, held to the fascia plate by screws 44 (FIGURE 1), carries terminals 16, 17 and 18 for connection to electrical supply and earth wires. The terminal 16 is connected directly to one power contact 19, the terminal 18 is connected directly to earth contact 20, and the terminal 17 is con- 3,143,616 Patented Aug. 4, 1964 nected to the other power contact 21 through switch contacts at 22 and a printed circuit connection 23. The socket for the lamp 12 is connected between the power contacts 19, 21 by means of printed circuit connections 24, 25, and the power contacts are also connected to spring tags 26, 27 at the sides of the block 24 where it interfits with the timing sub-assembly 15.

The switch contacts at 22 comprise a fixed contact 31 formed by a lug of a contact plate 28, and a cooperating movable contact 32 carried at the free end of a resilient electrically-conductive switch arm 29 that is secured at its opposite end to the block 24 by a screw 30. The switch arm 29 normally urges the contact 32 into engagement with the contact 31.

The timing sub-assembly is shown in FIGURES 3 and 4 and comprises a housing 33 that can be secured to the fascia plate 34 of the unit by a screw 35 (FIGURE 1). Disposed in the housing 33 is a temperature-responsive bimetallic strip 36 that carries mid-way along it a frame 37 in which is a spindle 38 projecting substantially at right angles to the broad faces of the strip. On the spindle 38 is a rockable pallet frame 39 bearing two pallets 40, 41 arranged to engage the teeth of a pallet wheel 42 mounted on a shaft parallel to the spindle 38. All the while the main switch contacts 22 are closed and the socket outlet is consequently live, the bimetallic strip is alternately heated and cooled causing the pallets 40, 41 to move to and fro in the direction of the longitudinal axes of the spindle 38 and pallet wheel shaft thereby releasing the teeth of the wheel 42 one after another at intervals so that the wheel can rotate a step at a time under the driving action of a coiled spring in a spring case 43 on the pallet wheel shaft.

' The bimetallic strip 36 is heated by a pair of resistors 45 that are bound to it. The resistors 45 are connected in series through a pair of switch blades 46, 47 and are supplied with current through wire pigtails 48, 49 connected respectively to terminal tags 50, 51 on the housing 33. The terminal tags 50, 51 are so disposed that when the timing sub-assembly is in place in the unit they engage respectively the aforementioned spring tags 27, 26 on the block- 24. Assuming that the main switch contacts 22 are closed, the resistors 45 will be supplied with current so long as the circuit is completed through the switch blades 46, 47. These switch blades are secured at 52, 53 to the housing 33, and the resistors 45 are electrically connected to the secured ends of the blades by pigtails 54, 55. The switch blades 46, 47 have free ends lying behind the bimetallic strip 36 as viewed in FIGURE 3, and the blades are of resilient material and set so that their free ends tend normally to spring apart. They are, however, pressed into contact with one another by the bimetallic strip when the latter is cold.

When heat is supplied to the bimetallicstrip 36 by the resistors 45, the strip tends to bend in a direction such as to cause its middle to rise up out of the plane of the paper, considering the assembly as viewed in FIGURE 3, and there comes a point at which the bending of the bi metal causes the free ends of the switch blades 46, 47 to move out of engagement with one another so breaking the heating circuit through the two resistors 45. The bimetal then cools and returns to its initial condition, there by re-engaging the switch blades 46, 47 so that the heating and cooling cycle recommences. The pallets 40, 41 move to and fro as the bimetal bends, permitting the wheel to move by one half tooth pitch when the bimetal is heated up and another half tooth pitch when the bimetal is cooled down. i

. The switch blades 46, 47 as well as an associated toggle spring 56 are shown enlarged in FIGURE 4. As viewed in FIGURE 4 the toggle spring 56 passes behind the switch blade 46 and through an aperture 57 in the switch blade 47, and its purpose is to cause the switch blades to break and make with a snap action. The spring 56 has a bend or hump 58 in the vicinity of the switch blade aperture 57, and it also has a tail portion 59 overhanging the bimetal 36. When the switch blades are in engagement as shown the tail portion 59 of the spring is free and the hump 58 is just above the switch blade 47 so that the spring tends. to urge the switch blade 47 toward the blade 46. When the bimetal 36 heats up and rises, considered as viewed in FIGURE 4, it engages and lifts the tail 59 of the spring thereby slightly relieving the pressure of the hump 58 on the blade 47 g the natural set or resilience of the blade 47 causes it to rise up past the hump 58 and then the hump acts to urge the blade 47 further in the upward direction away from the blade 46, the blades consequently separating with a toggle-type snap action. The reverse course occurs when the contacts are closed as the bimetallic strip cools down.

The setting of the bimetallic strip 36 is somewhat critical, it being arranged to lie, when cold, not flat but bowed at its middle in the direction away from the viewer as seen in FIGURE 3. To achieve the correct preset condition of the bimetal, it has one end received in a V-notch in one leg 60 of a U-spring 61, while the opposite end is engaged by one leg 62 of a' U-member 63. Endwise compression can be applied to the bimetal by an adjusting screw 64 accessible at the exterior of the housing 33, this screw being arranged to alter the spread of the legs of the U-member 63. The amount of how of the bimetallic strip'36 when preset in the cold condition is limited by a stop (not shown) behind the strip as viewed in FIGURE 3. The amount of bending that the bimetal can undergo, in the direction opposite to the initial bowl, when heated up is limited by a stop 65.

The pallet wheel shaft carries, behind the pallet wheel 42 as viewed in FIGURE 3, a gear 66 that is in mesh with a toothed sector 67. One of the push buttons 13 is an N button, and this, as seen in FIGURE 3, has a nosepiece 68 which engages the sector 67 when the button is pushed in thereby moving the sector angularly and rotating the pallet wheel 42. This rotation of the pallet wheel turns it to a predetermined angular position and winds up the pallet wheel spring; the rotation is in the reverse direction to that which occurs as the teeth are freed by the pallets 40, 41, and it is permitted to take place by yielding of the pallets in ratchet style, the pallet frame 39 turning slightly on the spindle 38 against the action of a pallet spring. The push button 13 is fitted to the outer end of a slide bar 69 that slide in a channel 70 in the housing 33 and is urged outwardly by a spring 71.

Also on the shaft of the pallet wheel 42 is a barrel 72 that lies alongside the resilient arm 29 of the main switch 22 when the unit is assembled as seen best in FIGURE 5. This barrel has on its periphery an axially extending rib 73 that acts as a cam lift in that, after a predetermined amount of angular movement by the pallet wheel 42 and barrel 72, it engages the switch arm 29 and cams it away out of contact with the fixed switch contact 31 to open the supply circuit to the socket outlet at the switch 22. It will be observed that the pallet wheel 42 has a tooth missing; the tooth is missing at a position on the periphery of the pallet wheel that reaches the pallets 40, 41 at the time when the rib 73 is about to engage the switch arm 29, the result being that at this point the pallet wheel moves an extra large step because of the missing tooth and the arm 29 is moved by the rib 73 sharply away from the contact 31 to achieve a quick, clean break of the main switch.

Accordingly, after the ON button 13 has been pushed in to start the mechanism, the electrical supply is connected to the socket outlet for as long as it takes the pallet wheel 42 to perform enough steps, under the control of the cycling bimetallic strip, for the barrel 72 to reach theposition at which the main switch 22 is opened by the cam rib 73 whereupon the main circuit is broken and the mechanism stops until such time as the ON button is again depressed. It has been found that a useful period of time during which to maintain the socket outlet live after depression of the push button 13 is about 45 minutes andthe mechanism can readily be set to achieve this.

The second push button 14 is an OFF button that enables the main circuit to be broken at will at any time. The OFF button is fitted to the end of a siled bar 80. that slides in a channel 82 in the housing 33 and is loaded by a spring 81. The slide bar 80 carries a pin 83 that lies under the tail of a pawl cam 84 (FIGURES 2 and 5). When the OFF button 14 is pushed in, the pin 83 raises the tail of the pawl cam 84 thereby rotating it about its pivot 90 and this causes a cam profile 91 on the pawl cam to press down the switch arm 29 and break the switch contacts 22. Both the slide bar 80 associated with the push button 14'and the slide bar 69 associated with the push button 13 pass through slots in .a transverse latch bar 98 arranged to slide endwise in the housing 33. The

is notched at 97 and when the button 14 is depressed the latch bar 98 is urged toward the left, as viewed in FIG- URE 3, by a double-legged spring 96, and the slot in the bar through which the slide'bar 69 passes has clearance as indicated at 94. The slide bar 80 of the push button 14 latch bar 98 moves a short distance to the left and engages in the notch 97 to latch the slide bar 80 in the depressed position. The slide bar 80 is released on the next occasion that the ON button 13 is pushed in; a cam face 93 on the slide bar 69 acts to force back the latch bar toward the right against the action of the spring 96 as the slide bar 69 moves in thereby unlatching the bar '80. That is to say when the OFF button has been used to open the main switch 22 the socket outlet can only be rendered live again by depression of the ON button 13.

' ployed to move a pair of pallets cooperating with a springdriven toothed pallet or escapement wheel. It is, however, possible, without departing from the scope of the invention to employ the movements of the bimetallic strip to drive a ratchet wheel in stepwise fashion through the intermediary of a pawl coupled to the bimetallic strip.

In that case, the ratchet wheel could be disposed with its axis parallel to the bimetallic strip, the pawl being in the form of a spring blade attached to the bimetallic strip and projecting generally at right angles to the broad faces of that strip. The ratchet wheel may be returned to a particular angular position each time the ON button is depressed in a similar manner to that in which the pallet wheel is turned and the spring wound in the embodiment hereinbefore described.

Since in the case in which a pawl and ratchet wheel is used it is not possible to obtain a striking action of the cam zrib upon the SWltChxZlI'IIl of'the main switch merely by omitting a tooth from the wheel, there may be a.

spring-loaded toggle arm operated by a striking pin rotating with the ratchet wheel to give a rapid and complete break of the main switch contacts.

The timing sub-assembly described is not restricted in its use to incorporation in a switch socket outlet but it can be used in other units, for example in a plug-in device that can be plugged into a standard 13 amp. outlet. If desired a unit in which the timing device according to the invention is employed can have a timing adjustor enabling the timed period for which the controlled main circuit is alive to be varied from, say, several minutes to several hours.

I claim:

1. An electrical timing device comprising a main switch, a heat sensitive element that moves in one direction upon heating and in the opposite direction upon cooling, electrical resistance heating means positioned to apply heat to said heat sensitive element when energized, an electrical energizing circuit for said resistance heating means which circuit is supplied with current through said main switch, a pair of electrical contacts in series in said energizing circuit, one of said pair being movable relatively to the other to open and close said circuit, operative connections between said heat sensitive element and said movable contact 'whereby said circuit is opened at said pair of contacts when said heat sensitive element has been heated to a predetermined extent and is closed again when said heat sensitive element cools down, a driving spring, manually-operable means for causing energy to be stored in said spring, a stepwise moving member coupled to said spring to be driven thereby, disengageable detent means engaging said stepwise moving member to hold it against movement by said spring and movable to and fro cyclically by said heat sensitive element upon alternate heating and cooling thereof to briefly disengage and reengage sequentially said stepwise moving member during each cycle of movement whereby said stepwise moving member makes a limited step movement under the effort of said driving spring during each brief disengagement by said detent means, and switch-operating means operatively associating said stepwise moving member and said main switch whereby said main switch is opened after a predetermined number of step movements of said stepwise moving member.

2. A device according to claim 1, wherein the stepwise moving member is a toothed escapement wheel and the detent means constitutes pallet means cooperating with the teeth thereof.

3. A device according to claim 2, wherein said manually-operable means comprises a 'depressible start button, the driving spring is a coil spring that can be wound up by reverse rotation of the escapement wheel, and operative connections are provided whereby depression of the start button causes reverse rotation of the escapement wheel to a predetermined angular position.

4. A timing device comprising a main controller having operative and inoperative conditions, a heat sensitive element that moves in one direction upon heating and in the opposite direction upon cooling, heating means positioned to apply heat to said heat sensitive element when operative, control means for said heating means, operative connections between said heat sensitive element and said control means to render said heating means inoperative when said heat sensitive element has been heated to a predetermined extent and to render said heating means operative when said heat sensitive element has cooled down, a driving spring, manually operable means operatively connected to said driving spring for causing energy to be stored in said spring, a stepwise moving member coupled to said spring to be driven thereby disengageable detent means engaging said stepwise moving member to hold it against movement by said spring, an operative connection between said detent means and said heat sensitive element whereby said detent means is movable to and fro in cycles by said heat sensitive element upon alternate heating and cooling thereof to disengage briefly and then reengage said stepwise moving member in that sequence during each cycle of movement and permit said stepwise moving member to make a limited step movement under the effort of said driving springs during each brief disengagement by said detent means, and operative connections between said stepwise moving member and said main controller whereby said main controller is caused to changeover from one output condition to the other after a predetermined number of step movements of said stepwise moving member.

- 5. A device according to claim 4, and comprising a bimetallic strip constituting said stepwise moving member is a rotatably mounted toothed escapement wheel and said detent means constitutes pallet means cooperating with the teeth of said wheel.

6. A device according to claim 4, and comprising a bimetallic strip constituting said heat sensitive element, an electrical resistance heater constituting said heating means, a supply circuit for said resistance heater, and electrical contacts in said supply circuit constituting said control means for said heating means.

7. A device according to claim 6, and comprising a spring member and a screwed adjustor acting on opposite ends of the bimetallic strip and subjecting it to endwise compression to preset it into a bowed condition in the cold state, the direction of bowing being opposite to that in which the strip normally bends as it is heated up.

8. A device according to claim 5, and comprising a manually-movable starting control member and operative connections between said starting control member and said escapement wheel whereby the escapement wheel is rotated, upon manual operation of said starting control member, to a particular angular position and in a direction opposite to that in which it is driven "by said driving spring thereby to wind up said driving spring.

9. A device according to claim 8, and further comprising a cam member which rotates with the escapernent wheel and is positioned to open electrical contacts of the main controller after said wheel has rotated a predetermined angular amount from said particular angular position.

10. A device according to claim 9, wherein said escapement wheel has a tooth missing at a point on its periphery that reaches said pallet means as the escapement wheel completes rotation through said predetermined angular amount from said particular angular position.

11. A device according to claim 4, and comprising a manual stop control member and operative connections between said stop control member and said main controller whereby operation of said stop control member causes changeover of the output condition of said main controller irrespective of the position of said stepwise moving member.

References Cited in the file of this patent UNITED STATES PATENTS 2,553,829 Morin May 22, 1951 2,584,725 McNairy Feb. 5, 1952 FOREIGN PATENTS 597,455 Germany May 25, 1934 

4. A TIMING DEVICE COMPRISING A MAIN CONTROLLER HAVING OPERATIVE AND INOPERATIVE CONDITIONS, A HEAT SENSITIVE ELEMENT THAT MOVES IN ONE DIRECTION UPON HEATING AND IN THE OPPOSITE DIRECTION UPON COOLING, HEATING MEANS POSITIONED TO APPLY HEAT TO SAID HEAT SENSITIVE ELEMENT WHEN OPERATIVE, CONTROL MEANS FOR SAID HEATING MEANS, OPERATIVE CONNECTIONS BETWEEN SAID HEAT SENSITIVE ELEMENT AND SAID CONTROL MEANS TO RENDER SAID HEATING MEANS INOPERATIVE WHEN SAID HEAT SENSITIVE ELEMENT HAS BEEN HEATED TO A PREDETERMINED EXTENT AND TO RENDER SAID HEATING MEANS OPERATIVE WHEN SAID HEAT SENSITIVE ELEMENT HAS COOLED DOWN, A DRIVING SPRING, MANUALLY OPERABLE MEANS OPERATIVELY CONNECTED TO SAID DRIVING SPRING FOR CAUSING ENERGY TO BE STORED IN SAID SPRING, A STEPWISE MOVING MEMBER COUPLED TO SAID SPRING TO BE DRIVEN THEREBY DISENGAGEABLE DETENT MEANS ENGAGING SAID STEPWISE MOVING MEMBER TO HOLD IT AGAINST MOVEMENT BY SAID SPRING, AN OPERATIVE CONNECTION BETWEEN SAID DETENT MEANS AND SAID HEAT SENSITIVE ELEMENT WHEREBY SAID DETENT MEANS IS MOVABLE 